In the traditional “pour up” of dental plaster being poured or otherwise inserted into a mold cavity defined by a bottom impression tray and sidewalls defined by a thin metal or wax footer, wetted crumbled paper or other materials are often used to prevent the dental plaster from undesirably entering onto areas of the mold cavity. For example, dental plaster often enters into the area between the wings of full arch impression trays. This is wasteful of the material and also requires extra time and effort in the molding process to remove the unwanted molding material from these areas.
Although the wetted crumbled paper or other materials are somewhat useful in helping to prevent the dental plaster from entering onto undesired areas of the mold cavity, this technique is messy, unscientific, and prone to substandard results.